1. Field of the Invention
The invention relates to a device and a method for the accurately metered transfer of printing ink between a fountain and a first ink roller. More particularly, the invention pertains to offset printing wherein a ductor roller is swiveled back and forth between a fountain roller and a first ink roller by a swivel mechanism that is independent of the main drive of the printing press.
2. Description of the Related Art
It has become known heretofore from German patent publication DE 39 35 215 A1 to use a ductor roller cam driven by an electromotor. The reference teaching is particularly adapted to fast-running, sheet-fed rotary printing presses, and adjusts the ductor lifting speed independently of the printing unit speed. That invention allows at high press speeds to maintain the ductor frequency below the dynamic limit of the ductor ink unit so as to satisfy the quality requirements of the color print.
The phase relationship between the movement of the printing unit and the movement of the ink ductor not being coupled is considered disadvantageous, and the inability to make a defined adjustment of the phase position of the ductor relative to the printing unit drive is also considered disadvantageous.
A further disadvantage is that the contact time of the ink ductor cannot be adjusted either at the fountain roller or at the first ink applicator roller.
According to the disclosure in German patent publication DE 23 41 510, an electromotor drives an inking unit control mechanism. Synchronization is effected by selecting a gearwheel that is driven by a main drive shaft, and an inking unit control mechanism following that gearwheel. A relative phase position of the inking unit relative to the main drive is adjustable and controlled through a pulse transducer, which senses the gearwheel position.
A disadvantage of that device is that the contact time of the ductor roller at the fountain roller and at the first inking roller is predetermined by a cam control and individual adjustments are not possible.
German Patent DE 33 24 448 C1 describes an ink metering device for letterpress and offset printing machines. The ductor roller of that device includes several mutually adjacent disks that are individually switched. The configuration leads to a problem whereby a plurality of adjusting elements and sensors are necessary for regulating and monitoring the individual disks. The resulting processing of the actuating and monitoring signals requires substantial computing capacity and a large share of available computer time. The mechanical problems resulting from the division of the ductor roller into individual disks include: severe soiling through the gaps formed in the division; a substantial amount of effort in the adjustment for the even contact of each disk at the fountain roller and at the inking roller; and exact balancing of each individual disk to avoid oscillations.